HUMAN-COMPUTER INTERACTION
SECOND EDITION
HUMAN-COMPUTER INTERACTION
SECOND EDITION
Finally the designer should consider the authors of help material as well as its users. It is likely that, even if the designer writes the initial help texts, these will be extended by other authors at different times. Clear conventions and constraints on the presentation and implementation of help facilitate the addition of new material.
There is in fact considerable debate between those who feel that a messaging system should impose conversational structures and constraints, and those who believe they should supply systems within which the participants can develop their own structures. It is argued that such user-defined structures are more likely to meet their needs, and the systems will be more flexible to accommodate changes in group working. The message systems based upon conversational models are the most constrained. Those offering structured messages, as we have described above, are towards the middle of the spectrum. The original email and bulletin board systems were at the other, unstructured, extreme, but lack sufficient features for the users to define their own structure. More modern systems from the 'user-structured' arena are developed from the bulletin board concept, but are more like a shared hypertext. The structure allowed by links and cross-references allows users to have subconferences and digressions, to annotate each other's messages and to post follow-on messages. An example of such a system is the Amsterdam Conversation Environment [71].
In Section 14.3.5, we discussed the process by which conversants obtain common ground. This grounding process is linked strongly with the types of channels
These are all constraints which are weaker in text-based compared with face-to-face interaction. For example, simultaneity in face-to-face conversation allows back channel responses. Even where, say, two participants can see each other's typed messages as they are produced, the nature of typing makes it all but impossible to type your message whilst looking for your colleague's 'back channel' response.
Altogether, the lack of grounding constraints in text-based communication makes it more difficult to obtain a common ground. It has also been found that email and text-based meetings are less effective at resolving conflicts than a face-to-face meeting.
Reviewability is another grounding constraint of communication, but this time one where text-based communication has the advantage over speech. You can of course tape speech, but it is far from easy to use this as a review mechanism.
Future computing environments promise to free the user from the constraints of stationary desktop computing, so researchers should focus on what applications maximally benefit from mobility. Highly portable devices, such as personal digital assistants, pagers and cellular telephones are starting to proliferate. The applications that the PDAs provide, however, are simple duplications of what we have on our desktops, and the other devices are still only used for simple messaging tasks. None of these devices takes into account the one thing that changes most when a user is mobile - position. Building applications that are customized to the user's physical and even emotional context can be of benefit in stationary modes of interaction as well. In Classroom 2000, students would provide anonymous feedback on their reactions to lecture pace and content. A context-aware classroom environment could signal the lecturer in some way if the majority of the students were either bored or feeling left behind.
This case study examines the design of pages for the World Wide Web. It highlights how the underlying limitations of the medium, the computer itself as well as the web protocols, constrain good page design. The intention of the study is to show how an understanding of the existing constraints can lead to pages that are much more informative, attractive and easier to comprehend, as compared with pages that are constructed without any thought for how they will be used. The specific lessons learned here are equally applicable across much of interactive system design. This case study is not intended to be a lesson in designing good web pages, and the issues highlighted here are not in any way comprehensive; instead, the intention is to demonstrate the considerations that should be borne in mind when designing.
Any system imposes its own constraints on the range of possible designs that it can support; some things are made easy, others become impossible, depending on the underlying system. Good design should recognize the strengths and limitations of the medium, and exploit the former whilst coping with the latter.
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